Closing the productivity yield gap
Global Planted Forests Congress:
Planted forests providing ecosystem services and
landscape restoration
Dublin, May 2013
Phil Polglase1, Don White1, Peter Clinton2, Tim Payn2
1CSIRO, Australia
2SCION,
NZ
Background
New Zealand plantations
•
•
•
•
1.80 M ha
Mostly radiata pine (1.60 Mha)
Average age: 15 years
Average volume: 242 m3/ha
Average MAI: 16 m3/ha/yr
• Exports to Australia, China, Japan (76% total) and others
• NZ$3.5 billion of export value (3.8% of GDP)
Australian plantations
• 2 million ha
• >$3 billion value (0.6% GDP).
• 1 mill ha softwood (mostly radiata pine) – average growth rate?
• 1 million ha hardwood (mostly blue gum) – anticipated to decline
by about 500,000 ha
Definitions of productivity gaps
Productivity
Actual
Non-limiting
(water, nutrients,
genetics)
Practically
achievable
Exploitable
Potential
Type 1 and Type 2 growth responses: Cumulative volume
Volume (m3/ha)
1,200
800
Control
Type 2
Type 1
400
0
0
10
20
30
40
Age (years)
Snowdon (2002)
Type 1 and Type 2 growth responses: Volume increment
Sustained
response: Site
resources increased
Unsustained
(G Site
x E x M)
response:
Current annual volume increment (m3/ha/yr)
40
resources not
increased
(M)
30
Control
20
Type 21
Type 12
10
0
0
10
20
30
40
Age (years)
Snowdon (2002)
Sustaining productivity responses
Productivity
Large and sustained
closure of yield gap is
typical of Type 2
response
Small and unsustained
closure of yield gap is
typical of Type 1
response
Sustained
closure
1R
2R
3R
Treated
Control
Unsustained
closure
Pattern of volume production for radiata pine
over three successive rotations in south Australia
Mean annual volume increment (m3/ha/yr)
40
6 plots
30
20
10
O’Herir and Nambiar (2011)
0
1R
2R
3R
Second rotation decline in blue gums plantations
in Australia
Volume (m3/ha)
160
1R
2R
120
80
40
0
CSIRO
WAPRES
White et al. (2013)
Weather, soil water and other (pests?)
causes (E. globulus in SW Australia)
300
Standing volume (m 3 ha-1 )
250
200
150
100
50
0
-50
-100
Site
residual
contribution soil water storage
contribution weather
observed2R
Two ways to increase stem wood yield
• Increase net primary production (carbon capture)
• Increase allocation of NPP to stem wood
NPP
= f (radiation, T, P, nutrition…)
Allocation
Turnover
Water use efficiency as an example
Managing stands for maximum water
use efficiency will a) maximize
productivity and b) minimise the water
cost (at least at larger scales)
… but there is an inescapable nexus
between productivity and risk
Volume increment (g) = WUE ( g kg-1) x Water use (kg) x harvest index (g g-1)
Adapted from Passioura (1977)
Water use efficiency – different definitions
all in g DM kg-1 H2O
Definition
Example
Total biomass DM
(ET)
Grain crops and
pastures (C3)
Instantaneous WUE
(effectively GPP of
sunlit leaves / E)
E. kochii
Above ground DM (E)
E. globulus / Acacia
mix
Pure E. globulus
WUE
Source
5 @ 1 kPa VPD
2 to 5 (3.5)
1 to 4
E. Globulus
Total biomass DM (E)
E. Kochii
Wood production (ET)
1.7
Oliver and Robertson
Wildy et al (2004)
Any number of
studies
Forrester et al (2009)
1
1.5 to 2.5
Wildy et al (2004)
E. globulus
1 to 5 m3 ML-1
Above ground DM
E. globulus
1 to 3.2
Unpublished data
White, Benyon,
Beadle
NPP (ET)
Native forests
2.8
3.2
Roxburgh UP
Budyko (??)
Total biomass increment (tonnes DM)
How do our plantations stack up?
30.00
E. cladocalyx
25.00
E. globulus
C. maculata
20.00
Limit - crop, pasture
15.00
10.00
5.00
0.00
0
2
4
6
8
10
12
14
Available water (ML or mm x 10-2)
Also see Dye (2000) South African Forestry J. 189: 17 to 26
…. and wood production
35.00
E. cladocalyx
Volume growth (m 3)
30.00
E. globulus
C. maculata
25.00
20.00
15.00
10.00
5.00
0.00
0
5
10
15
Available water (ML or mm x 10-2)
20
Upper limit to volume production in Australia
Mean annual volume increment (m3/ha/yr)
Can we model the
maximum, not the
average?
Upper limit to carbon production in Australia
Carbon increment (t/ha/yr)
NPP vs Transpiration (CABALA model)
Mean annual NPP (t C/ha/yr)
Polglase and Mendham (unpubl.)
Mean annual transpiration (mm)
Volume increment vs transpiration (CABALA model)
Mean annual volume increment (m3/ha/yr)
Polglase and Mendham (unpubl.)
Mean annual transpiration (mm)
Management to increase productivity
Blue gum (2 R decline)
• Wider spacing
• Drought resistant genotypes
• Fallow
Radiata pine
• Increase stocking
• Sterile genotypes
• Breeding and selection using
markers
• Residue retention
• Improved fertiliser management
• Residue retention
Conclusions
• Potential to increase productivity of radiata pine and in hardwood
plantations
• NPP is a better measure of productivity than volume
• Value is more appropriate measure for wood production
• Closing the yield gap needs to be sustained
• Wood production – closing the gap can increase risk
• Carbon sequestration – different risk profile
• Models and data a new opportunity for better G x E x M;
identifying causes
Further work
• Model verification (for NPP)
• Calibrate the model to the maximum, not the average?
• Spatial analysis of current productivity
• Spatial analysis of potential productivity
• G x E x M options to increase productivity
• Economic analyses
• Impacts of climate change